I think the big question for me would be whether this is something you’ll be doing 3 to 5 times a year or if this is a once-in-a-decade type event.
If you’re planning on trips multiple times a year (cruises, Las Vegas - i.e. to generally decadent food environments) then I would follow the advice of analyzing menus, looking for keto options, avoiding box lunch trips (or bring your own) etc. Keep your keto flag flying as best you can - and plan to learn more as you go.
But, if this is a big and very rare long planned trip - I would focus on (and let my decisions be made by) how I would feel if I skipped out on some of the things I had traveled so far to be around. I am not saying go wild and drop keto or anything. I am not saying have chocolate cake just because you are on your trip (you can get cake anywhere). But, if you talked yourself out of Fish and Chips in a fantastic downtown London restaurant (that prides itself on having great Fish and Chips) and had some boring old sausage and a side salad instead (to avoid carbs) - it might feel like a mistake after you’re back home. London also has some of the best Indian food that I have ever had - much better than I can find in California (you’ve paid quite a price to get this access - in this scenario, might be best to use it). Another example is that traditional Yorkshire Pudding is very non-keto but, if you have never tasted one, wouldn’t be back in London until 2025 and the restaurant has won the award for best Yorkshire Pudding in the UK for the last 5 years - well, you can guess my answer.
The other part is how you’ll handle pressure from other’s you are traveling with. If they know this is just the nth trip this year of many similar trips - I am sure they will be understanding.
If instead, everyone knows this is very rare trip, with an exotic destination, you’ll probably find people starting to get upset if too many restaurants/bars/pubs are “out of bounds”.
PS - Of course my suggestions about trying non-keto foods as part of a very rare trip assumes you are not on keto to keep a medical situation under control.